Vailant ecotek plus 438 - Fault 23 (f.23)

[ant2]

Please help:
Background:
Had an extension, plumber added UFH (new zone) and another new zone housing 2 towel radiators and 3 radiators (extension)

Hot water has been working throughout with no issues (all summer)

UFH worked for 2 days solid with no issues. This was turned off to test central heating. Central heating initially suffered Fault code 20,23,24.
Plumber believed it was due to air in the system after new radiators were added. Air was bled out ( over multiple attempts) and errors went away on main system.

Issue:
1.)
UFH - Now when the UFH is turned on, within 15minutes -> several hours it shuts off with "F.23) - Presume this is an airlock?

2.) New extension suffers from F.23, presume this could also be an airlock?

I have tried to run one radiator at a time and bleed it on the new extension and has not made any difference.
My only concern is I cannot find any results for others experiencing an F.23 error code from an airlock, yet the UFH worked fine initially for 2 days, which would make prognosis hold true.

Any suggestions and or tips here?
Any proper heating engineers from the Buckinghamshire area ? - High wycombe way

 

[ant2]

To help others, the dramatic amount of cycling you see in this video under https://www.diynot.com/diy/threads/...-slow-house-heat-up-please-help-bucks.509786/ and the F23 code was caused by a "faulty" pump.
I hadn't noticed as this had been getting "gradually" worse over the last 4 years, which is when I inherited it.

The pump sounded and appeared to be functioning fine, but it obviously was not operating "as it should".

I replaced it with a "dab - evoplus 80/180m pump". Even when limiting this pump to a 2M head the boiler cycling stopped (it just modulated), so it had an instant fix.
The daily F23 fault codes stopped and incidentally one of the reasons for this fault states "blocked/faulty pump". This provided further confirmation

Thoroughly impresses with the dab - evoplus 80/180m pump. It has a max output of 8M, I have set this on a 'proportional pressure' setting. This modulates the head (which can be displayed via the LCD) to the pressure it requires, so it's not constantly running at 8M when not needed.
From reviewing it appears tol operated between 3-6.5M, depending on requirement. With this pump the boiler is running at a full 38KW and no S23 or cycling observed. The rads are now finally all getting hot in minutes. I have never heard the boiler and pump raw so loud as they both crank up to full power.

I have a 22MM flow from the boiler that T's in to two pipe runs. A central heating run with 28MM -> 22mm, with 15mm radiator tails. The other T goes in to a 22mm hot water run to the airing cupboard. This contains 3 zones; hot water, an extension zone (5kw) and an UFH zone.

I will clock the boiler down for the summer setting to 15-20kw, as it will only be heating the 300L water cylinder.